Membranes and roofing materials of this type have a limited life time after which they need to be replaced. Traditionally, the used materials are brought to controlled landfill sites since the bitumen contained in these materials constitute an environmental hazard in that the bitumen may pollute the water such that special measures must be taken in order to store these types of materials.
In the art, it has been suggested in U.S. Pat. No. 6,039,914 to reuse these types of waste in a process where the bituminous materials are transformed into a crumble which crumble thereafter is shaped into a building block whereafter the building block is consolidated by for example infrared heating such that the bitumen will melt and thereby create the interior integrity of the building block. The asphalt crumble is created by introducing the bituminous waste material into a hammer mill wherein hammers are rotated such that they impact on the material and thereby shatter the waste material into small particle sizes. In practice, however, it has proven that due to the bituminous content of the waste materials and the sticky consistency of bitumen at certain temperatures, the hammer mill will be smeared with bitumen, and eventually there is a potential risk that the hammer mill all together will become clocked due to the sticky substance of the bituminous materials. Furthermore, reusing the bituminous materials by creating a crumble and thereafter shaping the crumble into building blocks by the addition of heat, is first of all a rather costly process, and moreover a market for disposing of a rather high number of the building blocks must be established. This even more so, as the building blocks made from a bituminous material do not exhibit high compressive or tensile strength characteristics and are therefore only usable in a very limited range of applications.
Another example is known from U.S. Pat. No. 5,201,472 wherein the scrap bituminous material is first shredded in a Telsmith shredder. After shredding the shredded material is passed through a sieve arrangement, where the material having sizes allowing it to pass the sieve is mixed with an aggregate, and “oversizes” left on the sieve is brought back to the shredder. In this way the mixing process involves two different apparatuses and method steps, i.e. a shredder and a mixer. The bituminous material is handled by the shredder, without any cleaning steps forseen, which may cause the shredder to clog up due to the sticky and adhesive nature of the bituminous material.